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Greenhouse effect
The Greenhouse effect refers to the change in the thermal equilibrium temperature of a planet or moon by the presence of an atmosphere containing gas that absorbs infrared radiation.http://www.ipcc.ch/pdf/assessment-report/ar4/syr/ar4_syr_appendix.pdf IPCC AR4 SYR Appendix Glossary Greenhouse gases warm the atmosphere by efficiently absorbing thermal infrared radiation emitted by the Earth’s surface, by the atmosphere itself, and by clouds. As a result of its warmth, the atmosphere also radiates thermal infrared in all directions, including downward to the Earth’s surface. Thus, greenhouse gases trap heat within the surface-troposphere system.A concise description of the greenhouse effect is given in the Intergovernmental Panel on Climate Change Fourth Assessment Report, "What is the Greenhouse Effect?" IIPCC Fourth Assessment Report, Chapter 1, page 105: "To balance the absorbed incoming solar energy, the Earth must, on average, radiate the same amount of energy back to space. Because the Earth is much colder than the Sun, it radiates at much longer wavelengths, primarily in the infrared part of the spectrum (see Figure 1). Much of this thermal radiation emitted by the land and ocean is absorbed by the atmosphere, including clouds, and reradiated back to Earth. This is called the greenhouse effect."Stephen H. Schneider, in Geosphere-biosphere Interactions and Climate, Lennart O. Bengtsson and Claus U. Hammer, eds., Cambridge University Press, 2001, ISBN 0521782384, pp. 90-91.E. Claussen, V. A. Cochran, and D. P. Davis, Climate Change: Science, Strategies, & Solutions, University of Michigan, 2001. p. 373.A. Allaby and M. Allaby, A Dictionary of Earth Sciences, Oxford University Press, 1999, ISBN 0192800795, p. 244. This mechanism is fundamentally different from the mechanism of an actual greenhouse, which instead isolates air inside the structure so that heat is not lost by convection and conduction, as discussed below. The greenhouse effect was discovered by Joseph Fourier in 1824, first reliably experimented on by John Tyndall in the year 1858 and first reported quantitatively by Svante Arrhenius in his 1896 paper.Annual Reviews (requires registration) In the absence of the greenhouse effect, the Earth's averageThe elusive "absolute surface air temperature," see GISS discussion surface temperature of 14 °C (57 °F) would be about -18 °C (–0.4 °F), the Black body temperature of the Earth Intergovernmental Panel on Climate Change Fourth Assessment Report. Chapter 1: Historical overview of climate change science page 97. Anthropogenic Global warming (AGW), a recent warming of the Earth's lower atmosphere as evidenced by the global mean temperature anomaly trend Merged land air and sea surface temperature data set , is believed to be the result of an "enhanced greenhouse effect" mainly due to human-produced increased concentrations of greenhouse gases in the atmosphereThe enhanced greenhouse effect and changes in the use of land Land Use, Land-Use change and Forestry, IPCC Special report SPM . The greenhouse effect is only one of many factors which affect the temperature of the Earth. Other positive and negative feedbacks dampen or amplify the greenhouse effect. In our solar system, Mars, Venus, and the moon Titan also exhibit significant greenhouse effects. The greenhouse effect causes more hurricanes to form, which are strong storms. Sources and Citations Category:Earth